Is your lighting bad or is it your textures?
Source filmmaker lighting is texture based. This means if your texture is low quality or uses your average DAZ materials you’ll run into a lot of issues.
or if it is a Workshop based model:
Search for the name of the object or character that you want to improve.
Once you find the folder, look up each texture individually or search for *_d.vtf
Verify that it is the body texture you want and then go to File > Export and then Save.
The .tga file can be opened in GIMP, Paint.NET and Photoshop.
My recommendation is:
Photoshop for Transparent textures.
DXT5 (compressed) and RGBA8888 or BGRA8888 (uncompressed).
Paint.NET for Opaque textures.
DXT1 and DXT5 (compressed) and RGB888 or BGR888 (uncompressed).
You can view the texture format by opening up VTF Editor again and clicking the Info tab.
Transparent textures often highlight the character model with masks. If you have Photoshop and a RGBA8888 or BGRA8888 texture, you can view its mask in the channels tab.
If your model turns dark after allocating a new texture then you probably are missing its alpha mask.
Open texture in VTF Editor > Export > Open the file in Paint.NET or Photoshop if Transparent.
Fixing your texture:
If your texture is low quality and you want to upgrade it, save it as .PNG and use waifu2x to increase its quality.
Settings should be Artwork, Highest and 2x.
You can keep it at 2x when you import into the .VTF but I recommend downscaling the image in Paint.NET through the Resize option to make it appear smoother. If you want to keep the 2x texture in its original upscaled size then you’ll have to upgrade all related materials otherwise there might be some ‘blocky’ texture issues.
To import your newly smoothed texture, open the old .VTF and click File > Import.
A new window will pop up with settings.
Make sure the file version is set to the correct one: 7.2 or 7.4
Input the right Normal and Alpha format.
You can view file details here.
Make sure compression quality is also set to High if you are working with a DX5 texture.
Here is a comparison of the end result:
Both are uncompressed BGRA8888 textures but the right one is improved.
Here is the texture in action:
In my Penny render I added a new skin texture on top of hers. Her face texture was brightened and smoothed to match with the new body texture.